The present invention relates inter alia to radiative fibers, their preparation and use in, e.g., lighting, display technologies, medical and cosmetic applications.
Organic electroluminescent devices, in particular organic light emitting diodes (OLEDs), have drawn much attention since two decades, because they have advantages over their inorganic counterparts in that they are, e.g., intrinsically flexible, and can be easily coated on large area by cheap methods, such as printing technologies like ink jet printing or screen printing. Therefore, organic electroluminescent devices are very promising devices for large area applications like general lighting and display technologies. Actually, OLED can already be found in marketed products such as the display of cell phones or digital cameras.
Another filed of application for organic electroluminescent devices is phototherapy. Phototherapy (also called light therapy) can be employed in a wide range of diseases and/or cosmetic (also called aesthetic) conditions. The therapy using light, either from LED or laser, is already being used to treat wounds, injuries, neck pain, osteoarthritis, the side effects of chemotherapy and radiotherapy, for instance.
Often the borders between therapeutic and cosmetic applications are vague and depend on individual circumstances and the assessment of a physician. Often therapeutic conditions are associated with cosmetic consideration. The treatment or prophylaxis of acne, for example, may have both therapeutic and cosmetic components, depending on the degree of the condition. The same accounts for psoriasis, atopic dermatitis and other diseases and/or conditions. Many diseases and conditions are associated with apparent implications which are often represented by a change in the visibility of a subject's skin, for instance. These cosmetic or aesthetic changes can often lead to psychological modifications resulting, at least in part, in serious diseases.
Some conditions or diseases may have an emphasis on cosmetic components, even if therapeutic elements may also play a role. Some of these are selected from anti-ageing, anti-wrinkle, the prevention and/or therapy of acne and vitiligo.
Many diagnostic tools or devices also often require light sources, e.g., in order to determine blood characteristics such as bilirubin, oxygen, or CO. In both cosmetics and medicine the skin is the main target to be radiated, but other targets of the human or animal body can also be accessed by phototherapy. These targets include, but are not limited to, the eye, wounds, nails, and internal parts of the body. Light can also be used in order to facilitate or support disinfection of wounds, surfaces of more or less solid objects, liquids, and beverages, for example. More or less solid surfaces as used herein include any surface with plasticity or elasticity which is not a liquid. Many objects fall in this category and comprise, e.g., nutrition, cuterly, instruments for use in hospitals and surgery and any other object that requires a disinfection. Even wounds of humans and animals can also be subsumed under this definition.
One of the primary effects of phototherapy is the stimulation of metabolism in the mitochondria. Certain wavelengths of light stimulate cytochrome c oxidase, an enzyme which is responsible for the production of the essential cellular energy in the form of adenosine triphosphate (ATP). ATP is required for cellular energy transfer in order to drive thermodynamically unfavoured biochemical reactions and as cellular energy storage. ATP can also act as signal molecule in order to modulate other biochemical molecules (e.g. reactive oxygen species and nitric oxide) that lead to ageing and cell death (oxidative stress). After phototherapy, the cells show an increased metabolism, they communicate better and they survive stressful conditions in a better way.
This principle can be applied for many medicinal therapeutic and cosmetic applications, such as wound healing, connective tissue repair, tissue repair, prevention of tissue death, relief of inflammation, pain, acute injuries, chronic diseases, metabolic disorders, neurogenic pain and seasonal effect disorders.
Another area of the application of light is the treatment of various cancers. In cancer therapy photodynamic therapy (PDT) plays an important role. In PDT light may be used in conjunction with a pharmaceutical. These therapies can be used to treat a variety of skin and internal diseases. In PDT, a light-sensitive therapeutic agent known as a photopharmaceutical is supplied externally or internally to an area of the body which is to be treated. That area is then exposed to light of a suitable frequency and intensity to activate the photopharmaceutical. A variety of photopharmaceutical agents are currently available. For example there are topical agents such as 5-aminolevulinic acid hydrochloride (Crawford Pharmaceuticals), methylaminolevulinic acid (Metfix®, Photocure). There are also injectable drugs used primarily for internal malignancies, including Photofin® (from Axcan) and Foscan® (from Biolitech Ltd). Often, the drug is applied in a non-active form that is metabolised to a light-sensitive photopharmaceutical.
In photodynamic therapy, the primary technique for supplying light to the photopharmaceutical is to project light of a suitable wavelength from standalone light sources such as lasers or filtered arc lamps. These sources are cumbersome and expensive, and are therefore only suitable for use in hospitals. This leads to inconveniences for the patient, and high cost for the treatment. High light irradiances are needed in order to treat an acceptable number of patients per day (for the treatment to be cost effective) and to avoid unduly inconveniencing the patient.
WO 98/46130 and U.S. Pat. No. 6,096,066 disclose arrays of LEDs for the use in photodynamic therapy. The small LED sources taught therein result in uneven light incident on the patient. Fabrication of arrays is complicated because of the large number of connections required. The devices shown therein are designed for hospital treatment.
GB 2360461 discloses a flexible garment which uses a conventional photodynamic therapy light source to produce light which is then transmitted through optical fibres. As such light sources are heavy, the device is not ambulatory and is limited to hospital use.
U.S. Pat. No. 5,698,866 discloses a light source using over-driven inorganic LEDs. A heat-sinking mechanism is required, and the device is suitable only for hospital treatment.
WO 93/21842 disclose light sources using inorganic LEDs. Although transportable, the device is not suitable for ambulatory use by a patient at home and clinical treatment is envisaged.
An essential prerequisite for the wide application of light in the fields mentioned above is the device. The commercial available systems nowadays are mostly based on lasers. However, theses systems are hospital based, i.e. stationary devices. In order to reduce costs and to increase convenience as well as compliance a portable home-use technology is required. In fact, some research has been devoted in this direction.
Organic electroluminescent devices have many advantages over their inorganic counterpart (light emitting diodes—LEDs) in that they are intrinsically flexible, and can be coated on large area by, for example, printing technologies, such as ink jet printing and screen printing. Furthermore they allow more homogenous irradiation as compared to LEDs.
Rochester et al. disclosed in GB 24082092 a flexible medical light source such as an OLED comprising flexible light emitting diodes on a flexible substrate and resulting diagnostic devices directed to monitor blood characteristics (e.g. levels of CO, oxygen, or bilirubin) and phototherapeutic devices for the treatment of ailments.
Vogle Klaus and Kallert Heiko disclosed in EP 018180773 a device for the treatment of skin. The device comprises an potentially flexible organic light emitting diode (OLED) as light source. The device can be integrated in clothes or plaster.
Attili et al. (Br. J. Dermatol. 161(1), 170-173. 2009) published a clinical open pilot study of ambulatory photodynamic therapy (PDT) using a wearable low-irradiance OLEDs in the treatment of nonmelanoma skin cancer, suggesting that OLED-PDT is less painful than conventional PDT with the added advantage of being lightweight, and therefore has the potential for more convenient PDT at home.
Samuel et al. disclosed in EP 1444008B15 an ambulatory device for the use in a therapeutic and/or cosmetic treatment, the device comprises an OLEDs and poly(p-phenylene vinylene) (PPV) is used as an example.
EP 1444008 discloses devices comprising OLEDs for the treatment of photodynamic therapy.
All of these devices used for the treatment are based on organic light emitting diodes (OLEDs).
However, state-of-the-art OLEDs use active metals, such as Ba and Ca, as cathode, and therefore they require excellent encapsulation to ensure an acceptable lifetime related to both storage and operation. For flat large area devices, appropriate encapsulation is even more critical, because defects in even small areas will lead to a total failure of the whole device. Further, in order to get good performance, particularly with respect to lifetime, OLEDs are usually designed to have a multilayer structure, wherein the different functions are optimized in individual layers. The manufacturing process of such devices requires, however, a more sophisticated manufacturing infrastructure, leading to high production costs and probably also low yields. It is highly desired to find a device, which is flexible and less insensitive to local damages.
Flexible fiber electroluminescent light sources are known in the art, as set forth, for example in U.S. Pat. No. 6,074,071, U.S. Pat. No. 5,485,355 and U.S. Pat. No. 5,876,863. Chemiluminescent fiber light sources are also known. These devices emit light when they are twisted to combine two chemicals contained in the fiber. The chemical reaction between the chemicals produces light while the chemical reaction proceeds for a few hours. However, these prior art chemiluminescent fiber light sources lack sufficient brightness, and are unable to achieve sufficient requirements for the medical or cosmetic use.
OLED fibers have been described recently in U.S. Pat. No. 6,538,375 B1, US 2003/0099858, and by Brenndan O'Connor et al. (Adv. Mater. 2007, 19, 3897-3900). Single OLED fibers and their use in lighting is described. However, the OLED fibers disclosed so far were aimed for display and general lighting applications.
Fiber OLEDs are also very interesting for the usage in so-called smart textiles. However, fiber OLEDs processed from solution remains still a technical challenge which is mainly due to the inhomogeneity of the surface of fiber and of the electrode coated on the fiber. This is because OLEDs are very sensitive to changes of the homogeneity of the surface and the thickness of the layers. For OLEDs, highly homogeneous layers are required. The thickness of layers in OLED is usually in the range between 20 to 80 nm causing a very narrow process window. For large pixels it is highly challenging to get thin films with a low roughness by employing a printing technique. The situation is even more complicated if the device is curved.
Furthermore encapsulation of such devices is still a very difficult task, because at least one reactive metal has to be used as cathode. Oxygen and humidity can inhibit or destroy the function of OLEDs.
There is, therefore, a need for the development of novel thin light sources without the drawbacks as described above.